The present invention relates to web cutting apparatus and more particularly to apparatus for removing and cutting a film strip from a cartridge.
U.S. Pat. No. 5,250,974 issued Oct. 5, 1993 to Iwasaki et al. shows a film cutter for removing and separating a film strip from a cartridge prior to processing the film in a film processor. The film cutter includes a carrier for holding the film cartridge. The carrier is biased to a home position and is moveable toward a switch when all of the film has been removed from the cartridge. A knife is mounted on the apparatus and when the carrier moves to trip the switch, the knife is activated to cut the film loose from the cartridge. It has been discovered that during film processing, using certain types of processing, that very slight changes in the velocity of the film will cause processing artifacts, in the form of lines, to appear in the processed film. The film cutter disclosed by Iwasaki et al. has the drawback that when the knife cuts the film, slight changes in the velocity of the film are generated, thereby potentially causing processing artifacts. There is a need therefore for an improved film cutting apparatus that avoids this problem.
The need is met according to the present invention by providing a film cutting apparatus for removing and separating a film strip from a cartridge, one end of the film strip being secured to a spool within the cartridge, that includes a carrier for receiving the film cartridge and moveable between a first position and a second position; a spring connected to the carrier for biasing the carrier toward the first position; a film drive for receiving a leading end of the film strip and pulling the film strip from the cartridge and then pulling the carrier away from the first position when the film strip is fully extracted from the cartridge; a sensor for sensing the movement of the carrier away from the first position and producing a signal in response thereto; and a knife mechanism mounted on the carrier for movement with the carrier and responsive to the signal for separating the film strip from the cartridge while the carrier is moving.
The present invention has the advantage that the cartridge and the mount for the film cutting apparatus undergo no relative motion during the cutting operation. Because the film cutting mechanism travels at the same speed as the film during the cutting operation, the film does not experience sudden stresses or velocity changes that could cause physical defects or processing artifacts.
Furthermore the film cutting apparatus of the present invention offers more flexibility in terms of cutting speed and shear angle since the cut does not impact the motion of the film and may occur over a longer period of time.